The present invention relates to secondary packaging and, in particular, to secondary packaging for containers which contain ready prepared meals.
Ready prepared meals are produced in aluminium foil or heat resistant plastic trays. The meal is cooked initially in the tray or inserted in the tray after an initial cooking stage. After this initial cooking, secondary packaging is then required so that the tray can be handled for distribution to and sale by the retail outlet.
It is known that plastics trays, such as those made from polyethylene treated by exposure to high energy electron or electromagnetic irradiation to increase its resistance to heat exposure, or those made from polypropylene, are generally only suitable for use as trays for ready prepared meals which are to be reheated by boiling or by microwave heating, since they tend to soften at temperatures of above 160.degree. C. The softening is particularly noticeable around the rim of such a tray which on being heated in a conventional oven, such as a fan oven, will tend to distort and crumple around the rim thus becoming wavy and very unattractive.
There thus exists a need for a plastics tray that can be packaged in a manner such that it can be heated in a conventional oven to temperatures in the range of from 160.degree. to 250.degree. C., or even greater without the rim or body of the tray either crumpling or collapsing.
One proposal for improving the heat resistance of a tray made from polyethylene which has been exposed to high energy electron or electromagnetic irradiation to increase its resistance to heat exposure, is to surround a tray made from the material with a blank to which the tray is joined at certain points, for example by gluing the blank to the underneath of the rim of the tray. The assembly of these trays and their protective blanks is thus a relatively time consuming operation which requires to be carried out very precisely if acceptable tray and blank assemblies are to be obtained.
We have now developed a secondary package for a container which contains a ready prepared meal, which does not suffer from the above disadvantages.